1. Field of the Invention
This invention relates to an optical recording medium.
2. Description of the Related Art
Card-shaped information recording media having excellent portability, such as magnetic cards and the like, are now widely being used. Recently, IC (integrated circuit) cards, optical cards and the like have also been proposed as large-capacity memories. In addition, hybrid cards provided, as disclosed in Japanese Patent Laid-Open Application (Kokai) No. 61-103287 (1986), by combining and integrating respective information recording media, i.e., a magnetic memory, an optical recording portion and an IC memory, have been proposed. In a hybrid card provided by combining an optical memory and an IC memory, it is necessary to dispose an optical recording layer and an IC module, which constitute the respective memories, within a specific card size (85.6 mm long, 54 mm wide and 0.68-0.84 thick).
In order to simplify the configuration of a device for performing at least one of recording of information in each of the IC module and the optical recording layer, and reproducing of information recorded in each of the IC module and the optical recording layer, it is preferable to dispose the IC module and the optical recording layer so as to prevent the respective recording/reproducing means of the respective memory units from interfering with each other.
For example, as shown in FIG. 7, in an optical card in which an optical recording layer 2 and a protective layer 4 are provided on a transparent substrate 1 in this sequence, and a recording/reproducing beam 11 is projected from the side of the transparent substrate 1, it is preferable that the electrode surface of an IC module 7 is exposed on a surface of the protective layer 4 opposite to the surface where the recording/reproducing beam 11 is incident. However, when, for example, an IC module having a thickness of about 0.5 mm is buried in an optical card, the back surface of the IC module is visually recognized via the transparent substrate 1, thereby degrading, in some cases, the appearance of the optical card. In addition, interconnection portions of the IC module are, in some cases, exposed to the back surface of the IC module where they can be easily seen, increasing the difficulty of maintaining of information recorded in the IC module.
In order to solve such a problem, Japanese Patent Laid-Open Application (Kokai) No. 8-142551 (1996) has disclosed an idea of hiding the back surface of the IC module of an IC-incorporating optical card with a masking layer. In this application, it is disclosed that, when a masking layer is provided on an outer surface of a hardened surface layer provided at the side of the IC-incorporating optical card where light is incident, the masking layer has poor adhesion to the hardened surface layer. In order to solve this problem, there is disclosed an IC-incorporating optical card which includes, as shown in FIG. 8, an optical recording portion 81, an IC module 82, a masking layer 83, a card substrate 84, a transparent protective layer 85 and a hardened surface layer 86, and in which a portion of the hardened surface layer 86 behind the IC module 82 is cut and the masking layer 83 is provided at the cut portion in order to hide the back surface of the IC module 82. However, since a process to cut the hardened surface layer 86 is required for each IC-incorporating optical card disclosed in this application, the process for manufacturing the optical card is complicated, thereby increasing the production cost. Furthermore, there is the problem that, when the hardened surface layer 86 is cut, fine cracks are, in some cases, produced at end portions of the cut portion and spread when the optical card is bent. In addition, the surface of the hardened surface layer 86 is, in some cases, damaged during cutting or due to dust produced during cutting.